Brush, particularly toohbrush and method for the manufacture thereof

ABSTRACT

Brush, particularly toothbrush and method for the manufacture thereof The present invention relates to a brush, particularly a toothbrush, comprising a brush head carrying bundles of bristles, and a handle with an injection-molded basic body which comprises a fastening section extending up to the brush head. To provide a brush that meets the hygienic standards as much as possible and can be manufactured in an easy way, it is suggested according to the invention that the bundles of bristles should be bonded to the basic body via a casting compound. Furthermore, the present invention provides a method for manufacturing a brush, particularly a toothbrush, comprising a brush head carrying bundles of bristles, and a handle, wherein the bundles of bristles are bonded to a basic body manufactured by injection molding from a thermoplastic after demolding of said basic body, and wherein the bond between the bundles of bristles and the basic body is formed by way of a casting compound that after its solidification is fastened to the basic body.

The present invention relates to a brush, particularly a toothbrush,comprising a bristle head carrying bundles of bristles, and a handlewith an injection-molded basic body which comprises a fastening sectionextending up to the brush head, through which the bundles of bristlesare bonded to the basic body.

Such a toothbrush is known from EP 1 142 505. In this prior art, abristle carrier in the form of a brush head platelet is first providedwith bundles of bristles. The bundles of bristles are first fastened tothe platelet-like bristle carrier, and the unit formed in this way isthereafter inserted into the brush head tray and fastened. As disclosedin EP 1 142 505, the fastening operation can be carried out by way ofwelding. The publication also discloses the gluing of the platelet tothe brush head tray. To this end the contour of the platelet mustexactly be matched to the contour of the brush head tray according to EP1 142 505. Moreover, the inner circumference of the brush head tray andthe peripheral rim of the platelet are made conical to achieve a contactthat is as tight and secure as possible between the brush head and theplatelet. This procedure is relatively complicated and cannot guaranteethat dirt will not get caught between the platelet and the rim of thebrush head tray. In an alternative variant, which is also known from EP1 142 505, adhesive is applied to the upper side of the brush head tocover the rim of the platelet. It might be that this will lead to acomplete sealing of the gap between the platelet and the brush head.However, this will result in an objectionable contouring on the surfaceof the brush, which also promotes the collection of dirt and bacteriaand is moreover detrimental to the cleaning efficiency in specificbrushes. Particularly in the case of toothbrushes attention must be paidthat the surface penetrated by the bundles of bristles is made as smoothas possible.

The teaching imparted in EP 1 142 505, however, adopts an idea thatshould in principle be welcomed, i.e. first to manufacture the basicbody by way of injection molding, which leaves the option to reproducealso complicated contours in an accurate way and at low costs, possiblyin a multi-component injection-molding process to mount functionalsurfaces or advertising prints or ornamental supplements on the basicbody. The manufacture of the basic body by applying relatively highinternal mold pressures will be completed before the bundles of bristlesare bonded to the basic body. It is only after the basic body has beenremoved from the injection mold that the bundles of bristles will beattached to the basic body. Nevertheless, it is not in the conventionalway that the bundle of bristles is introduced into a recess provided onthe brush head for this purpose and is equipped with a metallic anchor(conventional anchoring technique), but a relatively flat bristlecarrier is first equipped with bundles of bristles and is then attachedto the basic body. The bristle carrier can here be easily provided withbristle bundles of different sizes, which is rendered difficult in theconventional anchoring technique.

As has already been described above, the solution known from EP 1 142505 is however not optimal under hygienic and usability aspects.

It is the object of the present invention to develop the prior-art brushin this respect. Moreover, the present invention wants to provide amethod suited for manufacturing such a brush.

In consideration of the product-based problem the present inventionprovides a brush comprising a brush head carrying bundles of bristles,and a handle with an injection molded basic body having a fasteningsection extending up to the brush head through which the bundles ofbristles are bonded to the basic body through a casting compound brushdiffers from the generic prior art in that the bundles of bristles arebonded to the basic body through a casting compound.

As compared with the prior-art adhesive, the casting compound isadvantageous in terms of low viscosity so that possible free spacesbetween the basic body and the bundles of bristles or a basic bodycarrying said bundles of bristles are filled with the casting compound.This is true both for possible free spaces inside the brush head and forthe filling of voids and small free spaces or slots on the phaseboundaries of different elements of the brush head by the castingcompound. Furthermore, the casting compound is preferably used with avolume that fills all free spaces inside the brush head, wherebyhygienic standards are complied with in an improved way. The castingcompound is here applied with a technique differing from injectionmolding onto, on or around the fastening section.

Owing to the low-viscosity characteristics of the casting compound it isfurther possible to form the contour of the brush head either completelyor partly by way of the casting compound, i.e. also in cases where theexact molding of complex surfaces structures is required. Due to its lowviscosity and its material constitution the casting compound can beprocessed at atmospheric pressure or at a relatively small overpressure,so that in contrast to the bonding of the bundles of bristles by way ofinjection molding less equipment is needed and there is also no dangerthat the casting compound will travel along the filaments of bundles ofbristles beyond the outer surface of the brush head to be formed andwill glue the filaments of the bundles of bristles.

According to a preferred development of the present invention it issuggested that the casting compound should be positioned at least at theheight or level of the ends of the bundles of bristles at the fasteningside. This development is governed by the idea that the basic body formschannels for passing the bundles of bristles therethrough thatpreferably project beyond the basic body with their ends at thefastening side and form thickened portions that are formed at the end ofthe channels particularly preferably by fusion and rest on the channelsand can seal the same. The casting compound can be introduced for themanufacture of this preferred embodiment into a mold having surfacesthat are copied by the casting compound, so that the casting compoundforms the bottom surface of the brush head, i.e. the surface that inrelation to the brush head surface penetrated by the bundles of bristlesis provided opposite thereto.

In an alternative design the casting compound may also be bonded to thefastening section of the basic body and to a carrier shaped e.g. withthe contour thereof and/or the contour of the brush head. This designyields a sandwich structure consisting of fastening section, castingcompound and bristle carrier, with the ends of the bristle bundles atthe fastening side being positioned inside the casting compound andpreferably sealed or encapsulated by the same.

In a further alternative design, the casting compound forms the surfaceof the brush head penetrated by the bundles of bristles. In this designthe casting compound is tightly placed around the bundles of bristlesand seals the ends at the fastening side preferably on the phaseboundary between the fastening section and the layer formed by thecasting compound. The low viscosity of the casting compound yields asmooth surface penetrated by the bundles of bristles. Said bundles ofbristles are kept in the manufacture of said development preferably inchannels of a mold, which at any rate in a direction parallel to thebundles of bristles leaves some spacing between the fastening sectionand the mold surface. When said free space is filled with the castingcompound, it need not be feared due to the processing of the castingcompound at atmospheric pressure or at a just slightly raised internalpressure in the mold that the casting compound will enter into thechannels and glue the filaments of bundles of bristles above the surfaceto one another.

In the above-mentioned development in which the layer formed of thecasting compound is arranged between the fastening section and a bristlecarrier, it is possible to provide just a relatively thin layer ofcasting compound. The brush head can be produced with a very smallthickness. The casting compound is here provided between the fasteningsection and the bristle carrier just as a thin film. However, in thisdesign the casting compound can also flow around the rim area of thefastening section and/or the bristle carrier. Said preferred designexploits the special material constitution of the casting compound aftersolidification, with the provision that said constitution differs fromthe material constitution of the injection-molded basic body. Thus casesare possible where the casting compound after solidification showsrubber-like or elastomeric characteristics by virtue of which a softerimpact and/or cleaning surface can be created on the rim area of thebrush head. Likewise, it is feasible to incorporate special ingredientsinto the casting compound before casting the latter, said ingredientsbeing discharged during use of the brush. Cleaning additives are hereabove all envisaged that enhance the cleaning efficiency. In the case ofa toothbrush, additives may also be added that exhibit a therapeuticeffect in the oral cavity.

In contrast to the adhesive according to EP 1 142 505, which is justapplied in the area of the contact surfaces between bristle carrier andbasic body, the brush head tray is filled with a casting compound in theproduct according to the invention. Said compound solidifiessubstantially up to the rim of the brush head tray, preferably exactlyat the same height with said rim. As for the aim to fill the castingcompound “substantially” up to the rim of the brush head tray, thisshould be understood such that a small trough or a minor elevation ispossibly provided in the area of the rim of the brush head tray. Saidslight contour, however, is so insignificant that there will be nonoticeable difference with respect to the cleaning properties and thehygienic demands as compared with a brush having an entirely flatcontinuous, e.g. materially identical, surface in the area of the brushhead.

First of all, a volume of the casting compound may be introduced intothe brush head tray that is smaller than the volume of the brush headtray. The casting compound may then be filled substantially up to thelevel of the rim in that the bundles of bristles are introduced withdisplacement of casting compound with their end at the fastening sideinto the casting compound. Optionally, said bundles of bristles may herealso be fastened to a bristle carrier the insertion of which into thebristle head tray will displace casting compound, so that said compoundsolidifies approximately at the height of the rim of the brush headtray.

The casting compound preferably fills the whole brush head tray, wherebythe hygienic properties are improved and also the attachment of thebundles of bristles to the basic body.

A hot melt adhesive may be used as the casting compound. Suitable hotmelt adhesives show a very low viscosity at processing temperature, i.e.at a temperature below the melting point of the thermoplastic formingthe basic body.

As an alternative, the casting compound may be formed by an oligomersystem. Envisaged is here for instance a cyclic butylene terephthalate(CBT). Corresponding CBTs may be provided in powder-like or granularform. When heated, they will polymerize into thermoplastic PBT(polybutylene terephthalate). Likewise, the viscosity of such oligomersystems is relatively low. At the processing temperatures to be employedin this instance it is about at least ten times the viscosity of thethermoplastic forming the basic body.

Similar advantages are offered by casting compounds of the PUR system.Here, one-component or two-component systems may be used as castingcompound. A casting compound of polyurethane can be adjusted in terms ofprocessing time, color and hardness within wide limits and almost in anydesired way. The viscosity during processing is about 10 to 100 timeslower than that of the thermoplastic forming the basic body, which maye.g. be polypropylene.

The alternatives presented above with respect to the materialconstitution of the casting compound show the common feature of aconsiderably reduced viscosity under processing conditions. Thus, whilebeing filled into a mold for bonding the bristle bundle to the basicbody, the casting compounds can fill all of the free spaces and can alsoseal minor gaps to the outside that are e.g. exposed between the outercircumference of the bristle carrier and the inner circumference of thebrush head tray and/or within a grid-like bristle carrier and, withoutthe penetration of the casting compound, would provide cavities in whichdirt or germs might accumulate. Low viscosities within the meaning ofthe present invention are particularly viscosities of between 0.5 mPa·sand 10⁶ mPa·s, preferably between 10² mPa·s and 10⁴ mPa·s at processingtemperature. The processing temperature may be room temperature. Atelevated temperatures the processing temperature is below the meltingpoint of the thermoplastic forming the basic body. The thermoplasticforming the wall of the brush head tray is of relevance in the case ofbasic bodies which are injection-molded from several components.

For the solution of the method aspect according to the presentinvention, the present invention provides a method for manufacturing abrush, particularly a toothbrush, comprising a brush head carryingbundles of bristles, and a handle, wherein the bundles of bristles arebonded to a basic body manufactured by injection molding from athermoplastic after demolding of the basic body, which method differsfrom the previously indicated generic prior art in that the bond betweenthe bundles of bristles and the basic body is established through acasting compound that after its solidification is fastened to the basicbody.

In this procedure the casting compound after solidification willpreferably fill all cavities in the area of the brush head. The castingcompound can shape the brush head partly or however also predominantly.In the method according to the invention the casting compound ispossibly cast into an upwardly open mold accommodating the fasteningsection, in which it solidifies. As an alternative, the mold for formingthe brush head may also be substantially closed with inclusion of thefastening section. Such a closed mold will particularly be used wheneverthe casting compound is to form a substantial portion of the surface ofthe brush head, or even the whole surface of the brush head. While beingprocessed the casting compound shows a relatively low viscosity,particularly within the above-mentioned parameter limits. At atmosphericpressure or at a low internal pressure at the most, the casting compoundis introduced into the mold and is solidified therein. Thus the castingcompound can first be introduced into the mold under atmosphericconditions.

A mold within the above meaning may also be one formed by the fasteningsection itself. Said section may e.g. be shaped in the form of a brushhead tray which is introduced into the casting compound. When the endsof the bristle bundles at the fastening side are introduced into such abrush head tray, the casting compound will rise, namely preferably up tothe rim of the brush head tray. This creates a brush in which thesurface penetrated by the bristle bundles is entirely even and smooth.In matching the volume of the brush head tray with the displacementvolume of the introduced bundles of bristles optionally of the bristlecarrier carrying the bundles of bristles, the volume of the castingcompound to be filled in can here be determined such that it solidifiesat the same level with the rim of the brush head tray also in the areasbetween the bundles of bristles. Such solidification also between thebundles of bristles will also occur in the case of a bristle carrier oncondition that said carrier has an individual grid structure connectingthe bristle bundles to one another. The casting compound will flowthrough this open grid, which is sealed in the casting compound for theattachment of the bundles of bristles.

If the bristle carrier is shaped as a platelet with a closed surfacepenetrated by the bristle bundles, the casting compound will exclusivelypass into a gap between the bristle carrier and the basic body and willbe moved by displacement approximately up to the height of the rim ofthe brush head tray, with the casting compound preferably solidifyingafter a short period of time.

While in the above-described procedure the brush head tray is notcompletely closed in the manufacturing process, an alternativeconfiguration yields a cavity that is first closed and into which thecasting compound is introduced. To this end the bundles of bristles arefirst arranged in holes of a hole field plate, the hole field of whichis predetermined by the bristle attachment of the brush to be formed.This hole field plate is sealingly applied to the rim of the brush headtray. The cavity created thereby is filled with the casting compound. Atthe back side of the brush head tray oriented away from the bundles ofbristles, a filling hole may be formed for the casting compound. Aventing hole may possibly be provided at said place as well, throughwhich venting hole the air displaced out of the cavity can escape.However, the air can just as well exit through the holes of the holefield plate. The internal pressure inside the cavity is therebycontrolled such that the casting compound during solidification insidethe cavity molds the surface of the hole field plate without, however,penetrating into the holes to a considerable extent. Such a procedure ispossible owing to the relatively low viscosity and due to theapplication of only relatively low internal pressures in the cavity. Asa result of such a procedure, a smooth surface penetrated by the bundlesof bristles is obtained on the finished brush. After solidification thecasting compound may show a certain residual elasticity, so that theends of the bristle bundles at the fastening side are elasticallysupported within limits. Filling and sealing of the brush head tray doesnot require any complicated injection mold, as is needed in theprocedure according to U.S. Pat. No. 5,350,219.

The brush produced according to the method can thus be manufactured inan economic way, it meets the hygienic demands to be e.g. made in thecase of toothbrushes and has a brush head surface which could be calledeven and defect-free and which is penetrated by the bundles of bristles.

Advantages and details of the invention become apparent from thefollowing description of embodiments in combination with the drawing, inwhich drawing:

FIG. 1 is a longitudinal sectional view of a first embodiment of thepresent invention in the form of a toothbrush;

FIG. 2 is a longitudinal sectional view of a second embodiment of thepresent invention in the form of a toothbrush; and

FIG. 3 is a longitudinal sectional view of a third embodiment of thepresent invention in the form of a toothbrush.

FIG. 1 shows a basic body 1 which in the area of the brush head 2 formsa brush head tray 3 that is open towards the upper side of the brush andis defined by a surrounding rim 4.

FIG. 1 shows the basic body schematically at a time when a brush headplatelet 6 carrying a bundle of bristles 5 and forming a bristle carrieris not yet bonded to the basic body 1. The brush head platelet 6comprises channels through which the individual bundles of bristles 5are inserted. At the ends at the fastening side the bundles of bristles5 are provided with a thickening 7 that is produced by fusion of thebundles of bristles 5. The thickening 7 rests on the bottom side of thebrush head platelet 6, thereby closing the channels. A casting compound8 is applied to the surface formed in part by the thickening 7 and inpart by the bottom side of the brush head platelet. The brush headplatelet 6 prepared in this way is inserted together with the bundles ofbristles 5 into the brush head tray 3. The casting compound 8 is hereflowing inside the brush head tray 3, filling all cavities, and finallypenetrates into a gap between the circumferential surface of the brushhead platelet 6 and the basic body 1, until the casting compound 8 isapproximately at the same height as the rim 4 and the surface of thebrush head platelet 6. The casting compound 8 is solidifying at saidplace.

FIG. 2 shows an alternative embodiment in which the basic body forms asubstantially flat fastening section 9 which forms channels for holdingbundles of bristles 5. These bundles of bristles 5 are also fused attheir ends at the fastening side for forming thickenings 7. The basicbody 1 prepared in this way is subjected, projecting with the bundles ofbristles 5 downwards from the basic body 1, to a further treatment stepin which the casting compound 8 is applied to the bottom side of thebasic body and partly to the thickenings 7. After the casting compound 8has solidified, a shoulder-free surface is obtained on the bottom sideof the brush. The bottom side formed by the basic body 1 passes withoutany shoulders into the bottom side formed by the casting compound 8. Acorresponding structure is obtained at the face end of the brush.

In the alternative embodiment shown in FIG. 3, a hole field plate 10 isfirst equipped with bundles of bristles 5 that at their ends at thefastening side are provided with a thickening 7 by way of fusion. Thehole field plate 10 prepared in this way is mounted on the brush headtray 3 so that the hole field plate 10 rests on the rim 4 and seals acavity 11 predetermined by the brush head tray 3. The hole field plate10 is here sealing the brush head tray 3 on its rim. The castingcompound 8 is introduced into the cavity 11 through an introductionopening 12 recessed on the bottom side of the basic body 1. The castingcompound 8 solidifies inside the cavity 11 with inclusion of the ends ofthe bundles of bristles 5 at the fastening side and particularly of thethickenings 7. The casting compound thereby seals the ends of thebundles of bristles 5 at the fastening side, with the ends projectinginto the brush head tray 3. After solidification a shoulder-free evensurface that is penetrated by the bundles of bristles 5 is obtained onthe brush head 2, the surface being partly formed by the material of thecasting compound 8 and partly by the plastic component of the basic body1. The solidified casting compound 8 solidifies while molding thesurface of the hole field plate 10.

LIST OF REFERENCE NUMERALS

1 Basic body

2 Brush head

3 Brush head tray

4 Rim

5 Bundles of bristles

6 Brush head platelet

7 Thickening

8 Casting compound

9 Fastening section

10 Hole field plate

11 Cavity

12 Introduction opening

1. A brush comprising a brush head carrying bundles of bristles, and ahandle with an injection-molded basic body; the handle comprising afastening section extending up to the brush head, through which thebundles of bristles are bonded to the basic body, with a castingcompound (8).
 2. The brush according to claim 1, wherein the castingcompound is positioned at least at the height of the ends of the bundlesof bristles at the fastening side.
 3. The brush according to claim 2,wherein the casting compound seals the ends of the bundles of bristlesat the fastening side.
 4. The brush according to claim 1, wherein thecasting compound forms a surface of the brush head which is penetratedby the bundles of bristles.
 5. The brush according to claim 1, whereinthe casting compound forms the bottom surface of the brush head whichfaces away from the surface penetrated by the bundles of bristles. 6.The brush according to claim 1, wherein the casting compound is providedbetween a bristle carrier carrying the bundles of bristles and the basicbody.
 7. The brush according to claim 1, wherein the casting compoundforms the outer surface, preferably the rim area of the brush head, atleast in part.
 8. The brush according to claim 1, wherein the fasteningsection is formed in the manner of a brush head tray, and that thebundles of bristles are bonded to the basic body by way of the castingcompound filled into the brush head tray.
 9. The brush according toclaim 8, wherein the casting compound is filled substantially up to therim of the brush head tray.
 10. The brush according to claim 1, whereinthe casting compound is member selected from the group consisting of ahot melt adhesive, an oligomer system, a PUR system.
 11. The brushaccording to claim 8, wherein a plurality of bundles of bristles arefastened to a bristle carrier having a surface which is penetrated bythe bundles of bristles and is arranged substantially flush with the rimof the brush head tray.
 12. The brush according to claim 11, wherein thebristle carrier is configured as a plate-shaped component the contour ofwhich is matched to the contour of the rim of the brush head tray. 13.The brush according to claim 4, wherein the ends of the bundles ofbristles at the fastening side are held in the casting compound and thecasting compound forms the surface of the bristle head that ispenetrated by the bundles of bristles.
 14. The brush according to claim6, wherein the casting compound has solidified flush with the surface ofthe bristle carrier penetrated by the bundles of bristles.
 15. The brushaccording to claim 8, wherein the brush head tray is completely filledwith the casting compound.
 16. A method for manufacturing a brush havinga brush head carrying bundles of bristles, and a handle, in which thebundles of bristles are bonded to a basic body manufactured by injectionmolding from a thermoplastic after demolding of said basic body, whichcomprises forming the bond between the bundles of bristles and the basicbody with a casting compound that is fastened to the basic body aftersolidification of the casting compound.
 17. The method according toclaim 16, which comprises injection molding the basic body with a brushhead tray for accommodating the bundles of bristles, introducing thebundles of bristles with their ends at the fastening side into the brushhead tray, filling the brush head tray with the casting compound andsealing the ends of the bundles of bristles at the fastening side. 18.The method according to claim 17, which comprises introducing thecasting compound into the brush head tray, and introducing the bundlesof bristles at the end side of the brush head tray with displacement ofthe casting compound up to about the height of the rim of the brush headtray.
 19. The method according to claim 17, which comprises fasteningthe bundles of bristles to a bristle carrier penetrated by the bundlesof bristles, and introducing the bristle carrier into the brush headtray to such an extent that the casting compound is displaced into a gapbetween the bristle carrier and the basic body approximately up to theheight of the rim of the brush head tray.
 20. The method according toclaim 18, which comprises fastening the bundles of bristles to a bristlecarrier penetrated by the bundles of bristles, and introducing thebristle carrier into the brush head tray to such an extent that thecasting compound is displaced into a gap between the bristle carrier andthe basic body up to about the height of the rim of the brush head tray.21. The method according to claim 17, which comprises arranging theindividual bundles of bristles in holes of a hole field plate containinga hole field that predetermines the bristle attachment to be formed,sealingly placing the hole field plate on the rim of the brush headtray, and introducing the casting compound into the cavity closed by thehole field plate such that the ends of the bundles of bristles at thefastening side that project into the brush head tray are sealed in thecasting compound, and the casting compound solidifies with molding ofthe surface of the hole field plate.
 22. The method according to claim18, which comprises arranging individual bundles of bristles in holes ofa hole field plate having a hole field which predetermines the bristleattachment to be formed, sealingly placing the hole field plate on therim of the brush head tray, and introducing the casting compound intothe cavity closed by the hole field plate such that the ends of thebundles of bristles at the fastening side that project into the brushhead tray are sealed in the casting compound, and the casting compoundsolidifies with molding of the surface of the hole field plate.
 23. Themethod of claim 18 wherein the brush comprises a toothbrush.
 24. Thebrush of claim 1 comprising a toothbrush.